Shunting aid for railway signalling circuits



Oct. 29, 1963 w. M. PELINO ETAL 3,103,771

SHUNTING AID FOR RAILWAY SIGNALLING CIRCUITS Filed Jan. 25, 1957 IN VEN TORJ WILL/AM M PE'L/NO C OR/VE l (/5 14. 6141.1. AGHEI? 147' 7 GENE Y5 United States Patent 3,103,771 SHUNTING AID FOR RAILWAY SIGNALLING CIRCUITS William M. lelino, Garden Cit and Cornelius A.

Gallagher, Hicksville, NY, assignors to Servo Corporation of America, New Hyde Park, N.Y., a corporation of New York Filed Jan. 25, F957, Ser. No. 6365?] 6 Claims. (Cl. 246-28) Qur invention relates to an aid to railway-signalling devices and is particularly applicable to block-signalling systems.

In block-signalling systems, the presence of rolling stock on a particular section of track is relied upon to shunt a signalling relay, whereby automatic visual signals may be developed to reflect the presence of a train (or the lack of presence of a train) in a particular signalling block. With modern railroad rolling stock, such as lightweight cars, the development of adequate low-resistance shunt paths through the Wheels and axles of the rolling stock has become a problem, particularly in the presence of snow or ice on the track or in regions in which sand used for braking or starting has developed a vitreous film on the track.

It is, accordingly, an object of the invention to provide an improved railway-signalling device, and at the same time an improved means for boosting the eifectiveness of existing block-signalling systems.

It is another object of the invention to provide an improved track-shunting aid for block-signalling circuits.

It is a further object to provide a device of the character indicated which will not only improve the effectiveness but will also entail no modification of existing blocksignalling installations, so that even if the device of the invention should for some unaccountable reason fail to function, it will nevertheless not in any way impair the functioning of the existing block-signalling system.

It is a :general object to meet the above objects with extremely reliable equipment requiring a minimum of power supply and maintenance, yet materially improving the reliability of existing systems, and which will function regardless of weather extremes, and regardless of vitrified conditions of the rails.

Other objects and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings. In said drawings, which show, for illustrative purposes only, preferred forms of the invention:

FIG. 1 is a simplified diagram illustrating the spaced rails of a block-signalling system to which shunting aids of our invention have been applied;

FIG. 2 is an electrical diagram schematically illustratingd one application of a shunting aid of our invention; an

FIGS. 3 and 4 are diagrams similar to FIG. 2, but illustrating modifications.

Briefly stated, our invent-ion contemplates a device for application to existing block-signalling systems in order to improve the reliability thereof. The device comprises essentially a magnetic wheel trip mounted on a rail and developing a voltage pulse for each passing railroad wheel flange. Storage circuits respond to the voltage pulses to maintain an adequate control level, for wheeltrip pulses of sufiiciently rapid recurrence, reflecting a minimum train-speed response for the system. For train speeds above this minimum, a shunting relay is actuated to short-circuit the block-signalling winding.

Referring to FIG. 1 of the drawings, our invention is shown in application to a section of track comprising two 3,108,771 Patented Oct. 29, 1963 spaced elongated rails 10-11 of length corresponding to a conventional block-signalling section on a railroad. Insulation of rails 10-11 from each other and from the adjacent rails 1tl'1tl" and 1111 is suggested by discontinuities, indicated at a-b and at ab' in the drawing. Considering only the section covered by the rails 1011, the conventional block-signalling circuitry is illustrated by a low-voltage source 12 and currentlimiting resistor 13 exciting the rails 1011 at one end. At the other end oi the block section is the winding 14 of the conventional block-signalling circuit relay, which also includes an armature 15 and signalling contacts 16-17.

Normally, that is, in the absence of a train on the section 10-11, sufficient control voltage is developed from source 12 to actuate and hold the relay armature 15 in the position shown, thus determining completion of the clear circuit condition through the signalling contact 16. Theoretically, when a train enters the section, and regardless of the section end from which entry is made, the low-resistance shunting path (from one wheel, through its axle to the other wheel, and across both tracks 10-11) is relied upon to short out or shunt the voltage across the relay winding 14, thus causing the Winding 14 to drop out; the circuit through armature 15 is then completed to the contact 17, which determines the stop or caution condition of the signalling circuit.

In accordance with our invention, we apply to the existing system (represented by source 12, relay 14 and rails .1011) auxiliary means in the form of an allweather shunting aid whereby the presence of a train in the section may more reliably cause the relay 14 to function in the above-described manner. Occasionally, the shunting path, including the wheels and axles of passing rolling stock, is insufficient to enable relay 14 to drop out. As indicated generally above, this may be due to a vitrified surface condition on the rails, or to ice or snow, or merely to the fact that the rolling stock itself is too light in weight.

Preferably, we apply one of our shunting aids at each end of the block-signalling section 10-111, and We show in FIG. 1 the employment of two such aids 13*19. As indicated generally above, and as described in more detail in connection with FIG. 2, each of our shunting aids comprises a magnetic wheel trip 20' and associated integrating and amplifying means 21 for governing a relay "22 having contacts 23 connected either directly across the winding 14 or (as shown) to the rails 10-11, in close adjacency to the point of connection of the winding 14 thereto.

In FIG. 2, our shunting aid is shown to employ a magnetic wheel trip 20 of the variety discussed in greater detail in copending Gallagher-McDonald application.

Serial No. 627,330, filed December 10, 1956. Such wheel trip is characterized by magnetic-core means including a permanently magnetized core element 24, and an element 25 of flux-conducting material which, in conjunction with the web 26 of the rail section 10 to which it is applied, may establish at 27 a permanently polarized magnetic flux gap through which the flanges 28 of passing railroad wheels may pass; passage of a wheel flange through gap 27 modulates or varies the reluctance in the described magnetic circuit, thus causing win-ding means 29 (coupled to the magnetic flux path) to develop a voltage pulse for each passing wheel flange. As a practical matter, adequately strong voltage pulses :may be developed for wheel flanges on trains passing at speeds as slow as 5 miles an hour and ranging up to the top speeds of express trains.

The integrating circuit which functions from the wheel trip 20 is shown to utilize a vacuum-tube amplifier 30,

the output circuit of which includes the winding 22 of the relay utilized to shunt the signal-relay winding 14. In the form shown, voltage pulses developed by trip are rectified at 31 before application to a storage circuit comprising a capacitance 32, shunted by a leakage resistance 33, whereby positive voltage, adequate to overcome the effect of bias at 34, will be stored at 32 (and thus at the control grid of amplifier as long as voltage pulses of adequate repetition rate, reflecting at least minimum train speed, are developed at trip 30. Once the stored Voltage at 32 drops below the threshold of operation of amplifier 30 (meaning that the train has stopped, or that it is located between trips 19-20, or that it has left the block section), the charge on capacitor 32 will leak off to the extent that amplifier 30 will cease to conduct, thereby dropping out the relay 22.

In FIG. 3, we show application of our invention to an integrating circuit 35 based essentially on a transistor amplifier, employing the transistor 36. In order that the storage circuit 37-38 shall not be overloaded but, on the other hand, shall be loaded always with incoming voltage pulses of substantially the same level, we employ clipping means 39 interposed between the wheel pick-up device 20 and the amplifier 36. The clipping means is shown to be an extremely sensitive relay 3% which will pick up for wheel pulses of all the various magnitudes that may be developed by trip 20, regardless of the speed of passing trains within the design range of the equipment. The collector circuit of the transistor 36 is shown to include a relay 4G constituting the first stage of a twostage relay, in which the relay 22 may be considered the second stage. The arrangement in FIG. 3 happens to be one in which excitation of relay winding 40 determines the closing of relay 22 and thus the shunted condition of the track circuit; in the slight modification illustrated in FIG. 4, the excitation of relay 40 drops out the relay 22, but nevertheless also achieves the desired shunting.

In operation, the wheel pick-up 2t) develops a pulse output which will vary (in timing and in magnitude) with the speed and position of each wheel flange 28 cutting the field of the flux gap 27. For each pulse of at least threshold level, the relay39 functions to clip or to equalize the energy supplied to the capacitor 37; whenever relay 39 closes, charging current is applied through resistor 41 to capacitor 37, said resistor 41 serving to limit the charging current to protect the contacts of the sensitive relay 39. With a sufliciently low resistance value at 41, the capacitor 37 is usually charged in about 0.2 millisecond. Each sufficiently frequent impulse to the relay 39 keeps the charge on the capacitor to a peak, or at least above the threshold level determining conduction in the transistor amplifier 36, meaning that the relay 49 is continuously actuated; this condition continues until the train has passed the wheel trip 20. Capacitor 37 discharges only slightly between pulses, allowing enough base current to flow through the transistor to the emitter to keep the collector current at least at a level which will assure against drop out of relay 40. After all wheels of the train have passed, the storage circuit 3738 will discharge slowly through the base-emitter circuit of the transistor, thus allowing the collector current to fall ofl, and eventually to allow the output relay 40 to drop out.

While the train is still in the block section, and after it has passed, say, the trip 20, the multiple shunting paths developed by all wheels and axles of the train will be sufiicient to hold the shunted condition of the signalling relay, so that the existing block-signalling system will continue to indicate the occupied condition of the block section. When the train passes out of the block-signalling section 1fi11, there will be no more excitation of either of the pick-ups 19-20, and neither will there be any multiple shunt paths across the rails 10-11. This condition will permit restoration of potential from source 12 to the relay winding 14, thus enabling the circuit to l recondition itself to reflect the unoccupied condition of the block section 1fl1l.

It will be seen that we have described a relatively simple and fool-proof device which, in practice, has been found to be extremely reliable as an aid to existing blocksignalling systems; its installation in no way impairs the eificiency of any pro-existing block-signalling system. The device is unalfected by weather conditions, and particularly for the transistorized version of FIGS. 3 and 4, virtually no maintenance checking is necessary.

While we have described the invention in detail for the preferred forms illustrated, it will be understood that modifications may be made within the scope of the invention as defined in the claims which follow.

We claim:

1. In combination, a railway block-signalling circuit comprising two electrically insulated spaced rails of section length, a voltage source continuously connected to said rails at one end of said length, a signal relay having a winding energized from and continuously connected across said rails at the other end of said length, a magnetic wheel trip responsive to the passage of a wheel flange near one of said ends and developing a voltage pulse at the time of each such passage, and shunting means including storage means responsive to a predetermined minimum rate of wheel-trip pulses and directly electrically shunting said winding upon detection of said minimum rate.

2. In combination, a railway block-signalling circuit comprising two electrically insulated spaced rails of section length, a voltage source continuously connected to said rails at one end of said length, a signal relay having a winding energized from and continuously connected across said rails at the other end of said length, a first magnetic wheel trip responsive to the passage of a wheel flange near one of said ends and developing a voltage pulse at the time of such passage, a second magnetic wheel trip responsive to the passage of a wheel flange near the other of said ends and developing a voitage pulse at the time of such passage, and shunting means including separate storage devices respectively connected to said trips and responsive at each of said ends to a predetermined minimum rate of wheel-trip pulses, said shunting means directly shunting said winding upon detection of said minimum rate by one of said storage devices.

3. In combination, a railway block-signalling circuit comprising two electrically insulated spaced rails of section length, a voltage source continuously connected to said rails at one end of said length, a signal relay having a winding energized from and continuously connected across said rails at the other end or" said length, a magnetic wheel trip responsive to the passage of a wheel flange near one of said ends and developing a voltage pulse at the time of each such passage, integrating means responsive to the output of said wheel trip to develop a steady voltage for recurring wheel-trip pulses of at least a minimum periodicity reflecting a minimum speed to which said combination will respond, and means shunting said winding in [response to a voltage of predetermined level developed by said integrating means.

4. In combination, a railway block-signalling circuit comprising two electrically insulated spaced rails of section length, a voltage source continuously connected to said rails at one end of said length, a signal relay having a winding energized from and continuously connected across said rails at the other end of said length, a magnetic wheel trip responsive to the passage of a wheel flange near one of said ends and developing a voltage pulse at the time of each such passage, and shunting means including a storage device connected to the output of said wheel trip and responsive to a predetermined minimum rate of wheel-trip pulses to develop a control voltage, said shunting means further including a relay connected to said storage device and having contacts connected in shunting a,me,771

relation with said signal-relay winding and effective to shunt said winding in response to detection of said minimum rate.

5. The combination of claim 4, in which said shunting means includes a clipping device serving efiectively to develop from voltage pulses at the output of said wheel trip storageu'nput voltage pulses of a given level, so that regardless 0.1 the speed of passing wheel flanges, all voltage pulses to said shunting means will he of the same or substantially the same level.

6. The combination of claim 4, in which said shunting means includes a rectifier connected to polarize input pulses to said storage device.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN COMBINATION, A RAILWAY BLOCK-SIGNALLING CIRCUIT COMPRISING TWO ELECTRICALLY INSULATED SPACED RAILS OF SECTION LENGTH, A VOLTAGE SOURCE CONTINUOUSLY CONNECTED TO SAID RAILS AT ONE END OF SAID LENGTH, A SIGNAL RELAY HAVING A WINDING ENERGIZED FROM AND CONTINUOUSLY CONNECTED ACROSS SAID RAILS AT THE OTHER END OF SAID LENGTH, A MAGNETIC WHEEL TRIP RESPONSIVE TO THE PASSAGE OF A WHEEL FLANGE NEAR ONE OF SAID ENDS AND DEVELOPING A VOLTAGE PULSE AT THE 